How does an astrolabe work?

Answer 1

Answer

The astrolabe was used by the ancients ( III siecle B.C. in Greece)
for observing the relative positions and altitudes of celestial bodies.
In the Middle Age it become a navigational instrument by the addition
of tables of the Sun´s declination ( angular distance north or south of
the celestial equator), which permitted the sea Navigants to find their
latitude.
In its earlier form it consisted of a disk of wood suspended by a ring.
Around the disk edge were marked the degrees of the circle; a pointer
along which the sun or another star could be sighted was pivoted on a
center pin.
Later on the astrolabes were often made of metal with a plate with the
map of the stars and the zodiac circle on the reverse side. It was then
possible determine the time of the day: after measuring the sun´s altitude,
its position was noted on the circle of tfuyjfyjytjfhe zodiac, a line drawn to a circle
of hours showed the time.